Display device and method of manufacturing a display device

ABSTRACT

This invention relates to a display device comprising at least a first substrate ( 4 ), forming part of a display area ( 2 ), and at least one electrically controlled input device ( 3 ). According to the invention a first conductor pattern ( 8 ) for driving said display area ( 2 ) and a second conductor pattern ( 9 ) for tansmitting signals from said electrically controlled input  5  device ( 3 ) are arranged on said first substrate. The invention also relates to a method for manufacturing such a display device.

The present invention relates to a display device, comprising a displayarea and an electrically controlled input device, and to a method ofmanufacturing such a display device.

Different types of flat display devices are being used more and more indifferent applications. This includes smaller, handheld devices, such aspersonal digital assistants (PDAs), cellular telephones and displaycards. What is also common to such devices is that they, in addition toa display, include one or more components for inputting information tothe device. Such information input components may include a touch pad,buttons or the like. A touch pad detects the position of for example apointer, and may be used for the input of text or drawings. The touchpad may be arranged on the side of the display, or on top of the displayitself. Buttons may be used to activate different menus or to makechoices, and also for direct input of information, such as a push-buttonset on a cellular telephone. Many devices also have a combination ofinformation input components, such as both a touch pad and buttons,which is the case for many PDAs.

When it comes to display devices having a touch pad on top of thedisplay itself, i.e. included in the display area of the device, thereare several possible solutions. One alternative is to position aseparate touch pad in front of the display. Other alternatives are basedon measuring the difference in cell gap in the display area as a resultof local pressure by for example a stylus. Yet other alternativesinclude a stylus-like object including integrated electronics, such as acoil, the position of which can be determined by electronics positionedbehind the display.

However, the present arrangements of the display and the informationinput component or components described above have a number ofdrawbacks.

First, the connection between the different components, such as thebuttons, touch pad and display, may include connectors and flexiblefoils and may be quite expensive and difficult to manufacture. Moreover,in the case of the touch pad being positioned on top of the displayitself, this may further be disadvantageous in that it reduces theapparent optical performance of the display. An alternative solutionovercoming the above mentioned problems is therefore desired.

Hence, an object of the present invention is to achieve an improveddevice and method for integrating a display with information inputcomponent, thus overcoming the disadvantages of the prior art describedabove.

The above and other objects are at least in part achieved by theinvention as defined by claim 1. Hence, a display device is arrangedcomprising at least a first substrate, forming part of a display area,and at least one electrically controlled input device for user input tosaid display device, wherein a first conductor pattern for driving saiddisplay area and a second conductor pattern for transmitting signalsfrom said electrically controlled input device are both arranged on saidfirst substrate.

By arranging both conductor patterns on a single substrate, the inputdevice, for example comprising a touch pad and/or buttons, may be saidto be integrated on the same substrate as that used to form the displayin the display area itself. This offers a compact, easy-to-manufacturesolution and many assembly steps, such as interconnecting the displayarea and the input device, may be avoided.

Suitably, the at least one electrically controlled input device isarranged for user input of information to said display device. Theinformation may be used to control the display, or may be displayed bythe display. Preferably, said first and second conductor patterns aremanufactured from the same conductor material, which also facilitatesmanufacture and avoids any internal connector problems, whentransmitting signals from a conductor of one material to a conductor ofanother material. Suitably, said first and second conductor patterns aremanufactured from an essentially transparent conductor material, such asITO, ensuring proper functioning in the display area of the device.

Moreover, the display device further preferably comprises a secondsubstrate, being positioned in parallel with and on a distance from saidfirst substrate, wherein a layer of electro-optically active material,such as a liquid crystal material, is arranged between said substratesin the display area, and wherein at least one of said substrates aremanufactured from a flexible material. The flexibility of one of thesubstrates enables the distance between the substrates to be altered,due to mechanical pressure on an input device, which alteration is usedto enable activation of the button and/or touch pad being pressed.

In another preferred embodiment, a plurality of conducting particles,having a diameter smaller than the distance between said substrates, arearranged between said substrates, in the area of said input device. Thisenables activation of the input device at a lower applied force.Alternatively, in this case, both substrates may be comparatively rigid.The conducting particles preferably contact the second conductor patternon the substrate.

In order to further facilitate activation, external structures may beprovided, more preferably having a top area larger than the bottom area.Such structures are generally fastened at the outer surface of asubstrate.

The objects of this invention are also at least in part achieved by amethod for manufacturing a display device as described above, comprisingthe steps of providing a first substrate, forming a layer of conductivematerial on an inner surface of said first substrate, and patterningsaid layer of conductive material in order to generate a display areaconductor pattern and an input device conductor pattern on said firstsubstrate.

In the same way as described above, this provides for easy integrationof the display and the input device. Suitably, the step of patterningsaid layer of conductive material comprises the step of making saidconductive patterns in a single processing step, for example by means oflithography, which further facilitates manufacturing. The display devicefurther suitably comprises at least one external electrical connection,for accessing the display device from the outside, wherein an conductivepattern for transmitting signals from said external electricalconnection is simultaneously formed in the above-mentioned singleprocessing step, which also facilitates manufacturing, and limits thenumber of connections that need to be made during manufacturing.

The present invention will hereinafter be described in closer detail bymeans of preferred embodiments thereof, with reference to theaccompanying drawings.

FIG. 1 is a schematic perspective view of an example of a device inwhich the present invention is implemented.

FIG. 2 is a cross-sectional view of an input device area of the presentinvention.

FIG. 3 is a side view of two alternative external structures that may beused to increase the local pressure applied on an input device inaccordance with this invention.

FIG. 4 is a cross-sectional view of a CTLC display in which the presentinvention may be implemented.

FIG. 5 is flow chart illustrating the basic steps of this invention.

The present invention proposes an integrated display module, comprisingboth a display area and some means for information input. Such means mayfor example be a touch pad or buttons, being arranged to provide a userwith the possibility to input information to the display device, whichinput in some way affects the image to be displayed by the displaymodule. By means of the invention, such an integrated display module maybe manufactured in a simple and straightforward manner by applying theconductor pattern for driving the display area, on which the image is tobe displayed, and the conductor pattern for the information input meanson a single substrate.

A first embodiment of this invention will hereinafter be described withreference to FIG. 1. This first embodiment may for example be realizedas a PDA or some other display device. The term “display device” as usedherein shall be construed as a device comprising a display. Thisembodiment discloses a display device 1, having a display area 2 and anelectrically controlled input device 3. In the present example, theelectrically controlled input device 3 comprises a touch pad 5 and a setof buttons 6, for allowing user input of information to the displaydevice. In this example, the display area 2 and the electricallycontrolled input device 3 are arranged side by side on the displaydevice 1 and hence do not overlap. Furthermore, the display device 1comprises two substrates, a first substrate 4 and a second substrate 7,being arranged in parallel with each other and at a small distance fromeach other. In the display area, the small distance between the firstand second substrate 4, 7 is filled with an optically active material,such as a liquid crystal material. In the area of the electricallycontrolled input device 3, the distance between the substrates 4, 7 mayor may not be filled with a material, such as a liquid crystal material.However, in the present example at least one of the substrates 4 or 7should have sufficient flexibility to be deformed by touch input from afinger, stylus or the like.

According to the invention, the display device 1 also comprises adisplay area conductor pattern 8, being formed on an inner surface 4′ ofthe first substrate 4, and an input device conductor pattern 9, alsobeing formed on an inner surface 4′ of the first substrate 4, saiddisplay device being manufactured so that the two conductor patterns 8,9 are formed essentially simultaneously. The display area conductorpattern 8 is arranged to be used when controlling the display area inorder to provide a desired display pattern, and the input deviceconductor pattern 9 is arranged to transmit input information from theinput device 3 to a processor 10 or directly to the display area 2 to bedisplayed.

The input device conductor pattern 9 is suitably constituted by the samematerial as that used for the display area conductor pattern 8, forexample ITO, being a transparent material suitable for transparentelectrodes. The input device conductor pattern 9 and the display areaconductor pattern 8 are applied on the inner surface 4′ of the firstsubstrate 4 and are patterned in a single lithographic step. Suitably,the conductor patterns 8, 9 are formed by a single material layer formedin a single application step.

Regarding the electrically controlled input device 3, it may be embodiedso as to be for example a touch pad and/or one or more buttons, as isshown in FIG. 1. In both cases, information input is realized byapplying pressure on the selected area constituting the input device 3,so that electrical contact is established between the two substrates.This is made by mechanical movement by the inherent substrates. Theelectrical contact is induced either by physical contact between the twosubstrates 4, 7 (as stated above, the substrates 4 or 7 have sufficientflexibility to be deformed by touch input from a finger, stylus or thelike) or by an arrangement in which conducting particles are arranged inthe space between the two substrates, in the area of the input device.The latter arrangement is disclosed in FIG. 2 and this arrangement issuitable when the substrates to be used are comparatively rigid, sincethis embodiment limits the deformation of the substrate needed to obtainelectrical contact. The conducting particles may for example be in theform of conductive spacers, such as particles covered by a conductivematerial, such as plastic spheres covered with gold.

As is indicated above, the distance between the substrates, in the areaof the input device 3, may or may not be filled with a material such asliquid crystal, and in general, the dedicated area for the input device3 need not be filled with a liquid crystal material, and hence, thedisplay device is subdivided into a first and second cavity, essentiallydefined by the substrates 4, 7. However, in one embodiment of thisinvention, it is advantageous to connect the above-mentioned cavitieswith each other in order to allow a flow of liquid crystal materialbetween the display area 2 and the electrically controlled input device3. In this context it shall be noted that the term “cavity” as usedherein shall be construed as a limited space which may or may not be incontact with the ambient atmosphere.

Hence, when a button of the input device 3 is pressed or when a stylusis used to apply pressure on the touch pad of the input device 3, amechanical movement occurs. This mechanical movement may be used to pumpthe liquid crystal between the area of the input device and the displayarea, in order to erase an image on a bi-stable Liquid Crystal Display,such as a Cholesteric Texture Liquid Crystal display (CTLC), before newinformation is to be written on the display, as initiated by the signalfrom a button, resulting in said pumping action. The action of a CTLCdisplay is already known, and an example of such a display is disclosedin patent document U.S. 2003/0043317, the contents of which isincorporated into this application, and will therefore not be closerdescribed herein. A schematic drawing of a CTLC display having a displayarea 2 and two chambers, from which a flow can be induced and which alsoact as buttons in an input device 3, is further disclosed in FIG. 4.

Moreover, in order to facilitate activation of a button or the like by auser, the local pressure may be increased by an outside structure, beingapplied on an outer surface 4″ of the first substrate 4. This outsidestructure has a top end 11′ and a bottom end 11″, and the area of thetop end 11′ is larger than the area of the bottom end 11″, in order toincrease the local pressure on the first substrate 4, as applied by auser on the top end 11″ of the outside structure. Examples ofcross-sections of suitable outside structures to be used with thisinvention are disclosed in FIG. 3.

It is self-evident that the present invention may also be used indisplay devices in which the input device 3, such as a touch panel, isintegrated in the display area 2 itself. A few examples of such displaydevices are given above.

Alternatively, other conductor patterns, not primarily connected withthe function of the display or the input device, may be formed on thesame substrate. For example, a non-closed conductor loop may beincorporated in the periphery of the substrate. This loop may be used asa coil for transferring energy, such as electromagnetic radiation,between the display device and an electrical circuit in an externalinput device such as a stylus, which may be advantageous in certainapplications. Other inductive patterns may also be formed in accordancewith the invention.

The invention may also be used to provide conductive surfaces forcapacitive coupling for establishing communication between the displaydevice and an electrical circuit in an external input device such as astylus. Hence, the present invention is advantageous in that a pluralityof different components may be integrated onto a single substrate.

A method of manufacturing a display device according to this inventionwill hereinafter be described. The method comprises the step ofproviding 20 a first substrate 4. Thereafter a layer of a conductingmaterial, such as ITO, is applied 21 on an inner surface 4′ of the firstsubstrate 4. Thereafter, the method comprises the step of patterningsaid layer, for example by means of lithography, in order to achieve thedisplay area conductor pattern 8 and the input device conductor pattern9. Thereafter, the manufacturing process continues in a manner known perse, i.e. spacers are provided and a second substrate is arranged on topof the first substrate, a liquid crystal material is introduced at leastinto the display area of the display device, etc.

A plurality of application embodiments of this invention willhereinafter be described.

According to a first embodiment, the invention is implemented in aplastic CTLC-device, which in turn is implemented in a smart card, andfrom which information may be erased by the application of a mechanicalforce on a certain part of the display, as described above. In saidcertain part of the display, the input device is arranged in the form ofa button, and the button is integrated in the following way. Due to themechanical force which erases the display, the substrates 4, 7 toucheach other in this part of the display. In this part, a conduction layeris applied on both substrates 4, 7, i.e. on the surfaces thereof facingeach other, such that the applied mechanical force induces electricalcontact between the substrates. This electrical contact activates thebutton, and when the applied mechanical force is removed, the button isdeactivated, and thereafter, an electronic circuit may display newinformation on the display. More in general, the invention as describedabove may be used to integrate button functions with the display of anydisplay smart card.

According to a second embodiment, the invention is implemented in a PDA.Here, one part of the display device is not filled with liquid crystal.In the part filled with liquid crystal, the display is arranged, and inthe part not filled with liquid crystal, a touch panel and a pluralityof buttons are integrated by means of the inventive method describedabove. In the present case, one of the substrates 4, 7 extends beyondthe other one, at least in one direction thereof, in order toaccommodate an integrated circuit for driving the display, and anyadditional driving means for the display, being used to detect the userinput from the buttons and touch pad and display corresponding resultson the display. The integrated driving circuit mentioned above may beconnected to the first substrate 4, i.e. the substrate on which theconductor patterns 8, 9 are arranged. This connection may be realized bya chip-on-plastic technique, or by means of a flex foil technique.

According to a third embodiment of the invention, the present inventionis implemented in a twisted or super-twisted nematic liquid crystaldisplay device, essentially comprising a first and a second substrate 4,7 in between which a layer of nematic liquid crystalline material isarranged. The distance between the substrates defines the layersubstrates, and this measure may also be referred to as the cell gap ofthe display device. As described above, conducting particles, beingsmaller than the cell gap, may be introduced between the substrates.Hence, by pushing on the display, the top substrate may be slightlydeformed, so that an electric contact between the top and bottomsubstrate is achieved. In this embodiment, the conducting particles aredistributed in the display area of the display device, and hence thematrix, that is used to control the liquid crystal layer, may also beused to detect the position of the above contact. According to onealternative of this embodiment, the bottom substrate may be a glasssubstrate, and the top substrate may be a plastic substrate, such as a120 micron thick polycarbonate film coated with an indium-tin oxide(ITO) transparent conductor pattern according to the invention. The cellgap is maintained at 4.7 microns by means of lithographic spacers, andthe conducting particles may have a diameter of 4 microns and may beconstituted by plastic beads coated with gold. In a manner known per se,the inner surfaces of the substrates are also coated with conventionalalignment layers for liquid crystal alignment. According to a secondalternative of this embodiment, both the top and bottom substrate aremade from glass, and the cell gap is maintained by plastic beads, havinga diameter of 5 micron, and the conducting spacers are plastic beadscoated with gold, having a diameter of 4.5 micron.

It should be noted that the above-described embodiments of the inventionare not to be construed as limiting the invention, but are rather givenas examples of how the present invention may be utilized. A man skilledin the art will be able to design many alternative embodiments of thisinvention, without departing from the spirit and scope of thisinvention, as defined by the appended claims.

For instance it shall be noted that the invention is not limited toLCD-displays, but may in fact be used for any substrate-based displaydevice having at least one substrate. However, the invention isespecially suited for display devices comprising two substrates, andmore in particular to any display which is based on a cell having acertain cell-gap, whereby the display effect is confined between the twosubstrates. Also, it shall be noted that the invention is equallyapplicable in cases where the input device is arranged in a dedicatedarea not coinciding with the display area, and in cases where the areasfor the display and the input device partly or fully overlap.

It shall also be noted that the resistance of the material used for theconductor pattern of display areas is normally much smaller than theresistance of the material used for the conductor pattern of touch pads.One reason for choosing a material with a high resistance in the touchpad area is to increase the sensitivity. However, according to theinvention, it is advantageous to use the same material in both thedisplay area and the touch pad area. The desired increased resistancemay in this case be achieved by patterning the material layer in anappropriate way in order to increase the global resistance. Forinstance, fine lines will have a high resistance.

1. A display device comprising at least a first substrate, forming part of a display area and at least one electrically controlled input device, characterized in that a first conductor pattern for driving said display area and a second conductor pattern for transmitting signals ITom said electrically controlled input device are both arranged on said first substrate.
 2. A display device as claimed in claim 1, wherein said first conductor pattern and said second conductor pattern are arranged on a single side of said first substrate.
 3. A display device as claimed in claim 1, wherein the device further comprises a second substrate, being positioned in parallel with and at a distance from said first substrate, at least one of said substrates being manufactured from a flexible material, wherein a layer of an electro-optically active material is arranged between said substrates in the display area.
 4. A display device as claimed in claim 3, wherein a plurality of conducting particles, having a diameter smaller than the distance between said substrate, are arranged between said substrates, in the area of said input device.
 5. A display device as claimed in claim 4, wherein a conducting particle contacts the second conductor pattern on the substrate.
 6. A display device as claimed in claim 1, wherein said first and second conductor patterns are manufactured from the same conductor material.
 7. A display device as claimed in claim 1, wherein said first and second conductor patterns are manufactured from an essentially optically transparent conductor material.
 8. A method for manufacturing a display device as claimed in claim 1, comprising the steps of: providing a first substrate; forming a layer of conductive material on an inner surface of said first substrate; patterning said layer of conductive material in order to generate a display area conductor pattern and an input device conductor pattern on said first substrate.
 9. A method according to claim 7, wherein the step of patterning said layer of conductive material comprises the step of making said conductive patterns in a single processing step, for example by means of lithography.
 10. A method according to claim 8, wherein the display device further comprises at least one external electrical connection, for accessing the display device from the outside, wherein a conductive pattern for transmitting signals from said external electrical connection is simultaneously formed in the above-mentioned single processing step. 